Drying oven



Dec. 16, 1947, KRUSE 2,432,525

DRYING OVEN Filed July 6, 1942 Patented Dec. 16, 1947 UNITED STATES PATENT OFFICE Orlin O. Kruse, Oak Park, Ill., assgnor to American Can Company, New York, N. Y., a corporation of New Jersey lApplication July 6, 1942, Serial No. 449,938

The present invention relates to ovens for drying coated or lithographed metallic Sheets or the like and has particular reference to controlling the temperature of the interior of the oven.

An object of the instant invention is the provision in a drying oven of heat regulating devices wherein the. heat introduced into the oven is controlled and regulated at a place adjacent the heating devices and prior to its entrance into the o-ven so that burning and other heat damage to the work passing through the oven will be prevented.

Another object is the provision in such a drying oven of devices for heating the oven which include a pair of cooperating heating elements one of which isrcontrolled to augment the heat output of the other so that a predetermined required temperature may be constantly maintained in the oven.

Numerous other objects and advantages f the invention will be apparent as it is better understood from the following description, which, taken in connection with the accompanying drawings, discloses a preferred embodiment thereof.

Referring to the drawing:

Figure 1 is a sidel view of a portion of a drying oven embodying the instant invention; and

Fig. 2 is an enlarged fragmentary longitudinal section taken through that portion of the oven containing the heating devices, the view including a wiring diagram of the electric apparatus used in the oven.

As a preferred embodiment of the invention the drawing illustrates a portion of a sheet drying oven of the character disclosed in United States Patent 11,591,683, issued July 6,` 1926, to C. G. Preis. In such an oven freshly coated or lithographed sheets of tin plate or the like material are conveyed through a drying chamber in an upright or on-edge position while heated air is circulated through the chamber to dry the coating on the sheets.

In the instant oven the sheets to be dried are conveyed through a drying chamber A (Fig, 2.) which is enclosed by a sheet metal sectional shell or casing (Fig. 1) which includes a heat circulating section I2. The circulating section houses a` heating duct I3 which is formed in the upper portion of the circulating section and which communicates by Way of openings |5 with the drying chamber A. There preferably are two of these openings I5, one not shown but located at the right of the one shown in Fig. 2. The opening shown is the return opening for the heated air coming from the chamber into the duct. The other opening is the air entrance opening from the duct into the chamber.

The air within the chamber together with fresh air introduced into the chamber, is circulated therethrough by a continuously rotating fan I8 which is located within the heating duct I3. The fan is mounted on a horizontal shaft I9 journaled in bearings 2| formed in bearing brackets 22 located inside and also outside of the duct. Outside of the duct the fan shaft is driven in any suitable manner by an electric motor 23.

The air circulated through the drying chamber A- is heated by a pair of cooperating gas burners 3|, 32 which are located adiacent the return opening I5 of the duct I3. These burners are annular or ring shaped burners. Burner 3| is the main burner and burner 32 is a smaller auxiliary burner that fits within the main burner. These burners are disposed in ho-rizontal alignment with the fan I8 and are surrounded by a ilared shield 34 which directs the heat from the burners into the region of the fan.

A cooperating tapered deflector 35 spaced between the shield 34 and the fan I8 permits air, returning from the chamber A by way of the return opening I5, to mingle with the heat waves from the burners. This guides these air waves into the ian. The shield and the dellector are mounted on cross-beams 36 the ends of which are secured to the sides of the oven casing The main burner 3| is threaded onto the inner end of a hollow horizontal sleeve 4| which extends thro-ugh the end wall of the duct I3 and which is formed with a flange 42 bolted to this end wall. The outer end of the sleeve is connected by way of a pipe nipple 43 to a shut-off valve 44 which in turn is connected to a gas supply pipe 45, Pipe 45 leads from any suitable Supply 0f gas- The auxiliary burner 32 is threaded onto the inner end of a tubular body 48 that extends through the sleeve 4|. At the outer end of the tubular body an inlet opening 49 is located and this is surrounded by a tapered valve seat 5| for a shut-off valve 52 located within a valve casing 53 formed on the body 48. The valve 52 is formed on the lower end of a vertical valve stem 54 that extends up through a stuing box 55 threaded into the valve casing 53. The upper end of the valve stem is connected to a movable core 55 of a solenoid 51 secured to a bracket 58 bolted to the main burner sleeve 4|. The valve casing 53 is formed with a pipe connection 5| located above the valve 52 for a pipe that may lead from the same supply of gas hereinbefore mentio-ned.

Thus each burner 3|, 32 has a separate connection with the supply of gas and has a separate valve for regulating the flow of gas into the burners. These burners heat the air circulated through the drying chamber A as hereinbefore mentioned and, as the air passes through the duct, I3 toward the chamber, the fan thoroughly mixes the air. This overcomes and t prevents stratification. As the heated air leaves the fan stant temperature by Way of a thermo-electric couple 55 placed in the path of travel of the heated air circulated through the oven. For bestfref` sults it has been found that the temperature of the air is controlled best at a place nearthe dis- 1VW charge side of the fan I8. couple 55 is located at this place and is secured against displacement by a holder 66 that extends through the top of the duct I3.

The thermo-couple 55 is connected bywires 58, 69 to a conventional,temperature control relay Il bolted to the side ofthe oven casing- I I. The control relay is connected by a wire 'I3 to one side of the valve solenoid L The relayis connected further by a wire I4 to a suitable source of electric energy such as a generator l5. The generator is connected by way of a wire 15 to the opposite side of the valve solenoid 51.

Hence any change beyond a predetermined de-V gree in the temperature of the air leaving the fan i8, as detected by the thermo-couple 55, reacts through the control relay 'H onthe solenoid 51 and thus opens or closes the Valve 52 and thereby regulates the operation of the auxiliary burner32. Normally the solenoid 51' is in a deenergized condition so that the valve 52 remains closed against its seat 5l and thus cuts ofi the burner S2 from its source of gas. Thus normally the auxiliary burner is prevented from operating.

The main burner 3! remains in operation continuously and its control valve la is set to supply just suihcient gas to the burner to give off heat slightly less than the required predetermined temperature. Hence when*y the temperature of the 'airleaving the fan is at this slightly reduced heat, the thermo-couple 65 operates to energize the solenoid 5l and thus open the auxiliary valve 52.

This opening of the valve permits gas to How into the auxiliary burner 32. The gasimmediately ignites from the flame of the main burner 3l and thereupon the heat 'from the 'auxiliary burner augments the main burner heat. As soon as the temperature of the heated air hasreached the required amount, the thermo-couple `again operates to ole-energize the solenoid .5,1. IThis closes the auxiliary valve 52 and cuts off -the auxiliary burner 32. 1

In this manner the auxiliary 'burner 32 is brought into operation periodically with' anydeciency fluctuation of the temperature of .the heated air as it leaves the fan 18.1 It is. this close-up control of air temperature atthe. heat source that keeps the oven chamber ata .constant predetermined temperature. This prevents burning and other heat damage to coatingA on the sheets which pass through the oven for drying. 1

It is thought that the inventon'and many; of its attendant advantages will be understood from the foregoing descriptionfand it will be `apparent that various changes may be made in the form, construction and arrangement ofthe parts iwithout departing from the spirit and scopeV of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

Iclaim:

1. In an oven for drying coated metallic sheets advanced therethrough, the combination .fof means in said oven for'circulating heated air in The thermo-electric a continuous open stream through and entirely ,Within the oven in Contact with the moving sheets, a valve controlled main heating element disposed in said oven adjacent said air stream for providing the major amount of heat conl'tacting the sheets moving through the oven, a v.valve controlled auxiliary heatingr element also disposedin the oven adjacent said main heat- .ing` element for increasing the heat imparted to l.s'aidf;cir1culated.open air stream when the temperature thereof falls below the degree necessary .tomaintain the oven at the required sheet dryingtemperature, said circulating means being disposed in front of said heating elements, detector means located in said air stream within the oven at a point adjacent and in advance of said circulatingmeans for determining the temperature of the heated air` to be circulated in contact with the sheets, and means responsive to and operableby said detector means for actuating said auxiliary heating element to increase the heat imparted to the air stream by saidmain `heating element when the temperature of the heated air stream within the oven falls below said required degree.

2. In an oven for drying coated metallic sheets advanced therethrough, the combination of a fan located in said oven for circulating heated air in-a continuous open stream through and entirely vwithin the oven in contact Vwith the moving sheets, a valve controlled main burner disposedin said oven adjacent said air stream for providing the major amount of heat contacting the sheets moving through the oven, a valve controlled auxiliary burner also disposed in the oven adjacent said main burner for increasing the-.heat imparted to said circulated open air stream when the temperature thereof falls below the degree necessary to maintain the oven at the required sheet drying temperature, deector means disposed in the oven between said burners and said fan for directing the heated air stream to the'fan, said fan and said deflector means being disposed in front of said burners, detector means located in said air stream within the .oven at a'point adjacent and in advance of said fan for determining the temperature of the heated air to be circulatedin contact with thesheetS, and electro-mechanical meansY responsive to andoperable bysaid detector means for actuating said auxiliary. burner to increase the heat imparted to the air stream by said main burner when the temperature'of the heated air stream within the oven falls below said required degree.

. ORLIN O. KRUSE.

REFERENCES ohren f The following references are of record in the le of this patent:

Y UNITED STATES PATENTS Number 

